Age-related macular degeneration (AMD) is the leading cause of blind registration in the developing world and yet its pathogenesis remains poorly understood. However, there is increasing evidence to support a role for the immune system and oxidative stress, arising from an imbalance in the production and destruction of reactive oxygen species (ROS) such as superoxide anion, hydrogen peroxide and singlet oxygen, in disease progression. There is also clear evidence that photochemical sensitization of chromophores stored within lipofuscin in the retinal pigment epithelial (RPE) cells via absorption of both ultraviolet and visible light, leads to ROS generation and damage in the ageing eye. We have recently shown that all antibody molecules, regardless of species or antigenic determinant, have an intrinsic ability to generate a cascade of potent oxidants when presented with either a chemical or photochemical source of singlet dioxygen. The end product of the antibody-catalyzed water-oxidation pathway (ACWOP) is hydrogen peroxide and thus the implication for this pathway to play a role in AMD via interception of photochemically generated singlet oxygen is a real possibility and would lead to an increase in overall oxidative stress. We intend to investigate this hypothesis with the three following specific aims: 1. Specific Aim #1 To determine whether oxidants generated by the ACWOP, are damaging to passaged human RPE cells or primary cultured human RPE cells, in terms of cytotoxicity, apoptosis and expression of heat shock protein (Hsp) 27. 2. Specific Aim #2 To determine whether the ACWOP can be activated by photoirradiation of A2E-loaded RPE cells and whether such activation enhances photochemical damage to these passaged and primary cultures of human RPE cells. 3. Specific Aim #3 To determine whether the ACWOP when activated in whole blood, plasma and serum can affect RPE cell survival [unreadable] [unreadable] [unreadable]